Compositions comprising oxidized materials for sand casting and methods of preparation and use thereof

ABSTRACT

Compositions useful for green sandcasting are discussed, as well as methods of preparing and using such compositions. Binder compositions may comprise a carbonaceous material, an inorganic binding agent, and a high aspect ratio silicate, wherein at least one of the carbonaceous material or the inorganic material in the binder composition may be oxidized. For example, the inorganic binding agent may be oxidized with a ratio of ferrous iron (Fe2+) to ferric iron (Fe3+) less than 1.2. or less than 1. Green sand prepared from such binder compositions may exhibit a reduction in emissions during sandcasting.

CLAIM FOR PRIORITY

This PCT international Application claims the benefit of priority of U.S. Provisional Application No. 62/650,698, filed Mar. 30, 2018, the subject matter of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

Embodiments of the present disclosure relate generally to compositions useful for reducing emissions during casting, and methods of preparing and using such compositions.

BACKGROUND

Casting is a foundry process for preparing articles in which a heated liquid material, e.g., a metal, is poured into a mold and allowed to cool. The casted metal article is then released, or “knocked out,” of the foundry article. Casting produces a variety of emissions, including hazardous air pollutants such as volatile organic compounds (VOCs) released during the pouring, cooling, and knocking out phases of casting. Safety and environmental concerns are associated with VOCs, including benzene, toluene, ethylbenzene and xylene (commonly referred to as “BTEX”), carbon monoxide (CO), and methane (CH₄) released during casting. These emissions create certain safety and environmental concerns.

The emissions from the casting process relate to the compounds used to create the mold, e.g. green sand compositions formed from binder compositions. Therefore, is desirable to create green sand compositions from materials that may reduce the amount of harmful emissions produced during casting while maintaining the performance of mold and the casting quality of the casted article.

SUMMARY

The present disclosure includes compositions useful in sand casting, including green sand casting, preparation of such compositions, and methods of use thereof.

For example the present disclosure includes a binder composition comprising a carbonaceous material, and an inorganic binding agent, wherein at least one of the inorganic binding agent or the carbonaceous material may be oxidized. According to some aspects of the present disclosure, the binder composition may comprise from about 0.1% by weight to about 20.0% by weight of the carbonaceous material. For example, the binder composition may comprise from about 2% by weight to about 22% by weight, from about 5% by weight to about 20% by weight, from about 7.5% by weight to about 17.5% by weight, or from about 10% by weight to about 15% by weight of the carbonaceous material, relative to the total weight of the binder composition. In some examples, the carbonaceous material may comprise coal, lignite, lignite coal, leonardite, graphite, anthracite, cellulose, or a combination thereof. In some examples of the present disclosure, the binder composition may comprise from about 70% by weight to about 90% by weight of the inorganic binding agent, such as from about 75% by weight to about 88% by weight, or from about 80% by weight to about 85% by weight. Exemplary inorganic binding agents include sodium bentonite, calcium bentonite, or a mixture thereof. In some aspects of the present disclosure, the inorganic binding agent may be oxidized such that a ratio of Fe²⁺/Fe³⁺ of the inorganic binding agent is less than 1.2, such as, e.g., less than 1.0, less than 1, less than 0.9, or less than 0.8.

According to some aspects of the present disclosure binder composition may comprise a high aspect ratio silicate. In some aspects of the present disclosure, the binder composition may comprise from about 0.1% by weight to about 5.0% by weight of the high aspect ratio silicate, with respect to the total weight of the binder composition, such as, e.g., from about 0.3% by weight to about 4.5% by weight of the high aspect ratio silicate, with respect to the total weight of the composition, such as, e.g., from about 0.5% by weight to about 4.0% by weight, from about 1% by weight to about 3.5% by weight, or from 3.5% by weight to about 5.0% by weight. In some aspects of the present disclosure, the high aspect ratio silicate may comprise mica or talc. Additionally or alternatively, the high aspect ratio silicate may comprise muscovite, paragonite, lepidolite, phlogopite, biotite, or a combination thereof.

The present disclosure further includes a green sand composition comprising the binder composition described above, or elsewhere herein, and an aggregate. The aggregate may comprise silica sand, zircon sand, an aluminosilicate, or a mixture thereof.

The present disclosure further includes methods for preparing a foundry composition. For example, the method may comprise preparing a binder composition by oxidizing a carbonaceous material, and combining the oxidized carbonaceous material with an inorganic binding agent. The method may further comprise combining the oxidized carbonaceous material with a high aspect ratio silicate before, after, or at the same time as combining the oxidized carbonaceous material with the inorganic binding agent. According to some aspects of the present disclosure, oxidizing the carbonaceous material comprise treating the carbonaceous material with an oxidation agent, such as, e.g., soda ash, hydrogen peroxide, ozone, or a combination thereof. In some aspects of the present disclosure, a ratio of Fe²⁺ to Fe³⁺ of the inorganic binding agent may be less than 1, such as, e.g., less than 0.9, less than 0.8, less than 0.7, less than 0.6, or less than 0.5. The method may further comprise adding an aggregate and water to the binder composition to form a green sand composition. According to some aspects of the present disclosure, the green sand composition may have a. green compression strength ranging from about 21.5 N/m² to about 30.5 N/m², such as, e.g., from about 22.5 N/m² to about 30.0 N/m², or from about 24.0 N/m² to about 27.5 N/m². Additionally or alternatively, the green sand composition may have a green shear strength ranging from about 2.5 N/m² to about 3.7 N/m², such as, e.g., from about 2.6 N/m² to about 3.6 N/m², from about 2.9 N/m² to about 3.5 N/m², or from about 3.1 N/m² to about 3.4 N/m².

The present disclosure further includes methods for molding an article. For example, the method may comprise introducing a heated material into a mold wherein the mold comprises any of the binder compositions and/or green sand compositions described above or elsewhere herein, and allowing the heated material to cool. The method may further comprise the mold releasing less than 0.15 mg/g BTEX after introducing the heated material into the mold, such as, e.g., less than 0.12 mg/g, less than 0.10 mg/g, less than 0.08 mg/g, less than 0.06 mg/g, or less than 0.05 mg/g.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various exemplary aspects of the disclosure, and together with the description, serve to explain the principles of the present disclosure.

FIG. 1 is a graph of BTEX emissions measured from green sand compositions, as discussed in Example 2.

DETAILED DESCRIPTION

Particular aspects of the present disclosure are described in greater detail below. The terms and definitions provided herein control, if in conflict with terms and/or definitions incorporated by reference.

As used herein, the terms “comprises,” “comprising,”'or any other variation thereof are intended to cover a non-exclusive inclusion, such that a process, method, composition, article, or apparatus that comprises a list of elements does not include only those elements, but may include other elements not expressly listed or inherent to such process, method, composition, article, or apparatus. The term “exemplary” is used in the sense of “example” rather than “ideal.”

As used herein, the singular forms “a,” “an,” and “the” include plural reference unless the context dictates otherwise. The terms “approximately” and “about” refer to being nearly the same as a referenced number or value. As used herein, the terms “approximately” and “about” should be understood to encompass ±5% of a specified amount or value.

Aspects of the present disclosure include hinder compositions comprising inorganic binding agents, e.g., clay minerals, and carbonaceous materials, wherein the inorganic binding agent(s) and/or the carbonaceous material(s) are at least partially oxidized, and methods of preparation and use thereof. For example, the binder compositions may be used in green sand casting, e.g., combining the binder composition with an aggregate such as sand.

Compositions according the present disclosure may comprise one or more inorganic binding agents. Exemplary binding agents include, but are not limited to, natural and synthetic clays, such as, e.g., bentonite. Bentonite is a phyllosilicate clay, comprising predominantly smectite minerals, e.g., montmorillonite. The different types of bentonite are generally named after the dominant compositional element, such as potassium bentonite, sodium bentonite, calcium bentonite, and aluminum bentonite. For example, the composition (e.g., binder composition) may comprise at least one bentonite chosen from sodium bentonite, calcium bentonite, potassium bentonite, lithium bentonite, aluminum bentonite, or a mixture thereof. Bentonite may provide plasticity to the binder composition. In some examples, the inorganic binding agent may comprise a mixture of bentonite and another inorganic binding agent.

The inorganic binding agent(s) may be obtained from any geographic region or regions. For example, inorganic binding agents according to the present disclosure may be obtained from the western, mid-western, and/or southern regions of the United States (including, but not limited to, Wyoming, Montana, South Dakota, Indiana, Michigan, Wisconsin, Ohio, Mississippi, and Alabama), Greece, Germany, Turkey, Italy, Bulgaria, China, India, Russia, or Brazil, among other countries and geographic regions worldwide. Clays from different geographic regions may vary in chemical composition. For example, certain clays obtained from India may have a higher level of oxidation compared to clays obtained from the United States.

According to some aspects of the present disclosure, the inorganic binding agent may comprise at least about 75% by weight bentonite, such as, e.g., from about 75% by weight to 100% by weight bentonite. For example, the inorganic binding agent(s) may comprise at least 80%, at least 85%, at least 90%, or at least 95% by weight bentonite, e.g., from about 85% to about 95% by weight, or from about 90% to about 98% by weight bentonite.

In some exemplary binder compositions according to the present disclosure, the total amount of inorganic binding agent may range from about 70% by weight to about 90% by weight, with respect to the total weight of the composition, such as from about 75% by weight to about 88% by weight, or from about 80% by weight to about 85% by weight. For example, the binder composition may comprise about 75%, about 80%, about 83%, about 85%, or about 88% by weight of inorganic binding agent, with respect to the total weight of the binder composition.

According to some aspects of the present disclosure, the inorganic binding agent may be at least partially oxidized. For example, the inorganic binding agent(s) may be combined or exposed to one or more oxidation agents including, but not limited to hydrogen peroxide (H₂O₂), oxygen (O₂), ozone (O₃), or soda ash (sodium carbonate) (Na₂CO₃). In some examples, the oxidation agent(s) may be in aqueous solution. The inorganic binding agent(s) may be combined with the oxidation agent(s) by any suitable method that allows for reaction. For example, the oxidation agent(s) may be mixed with the inorganic binding agent(s) at a weight ratio ranging from about 1:100 to about 1:10 (oxidation agent:inorganic binding agent), such as, e.g. from about 1:75 to about 1:15, or from about 1:50 to about 1:25. In some examples, the oxidation agent(s) may be mulled together with the inorganic binding agent(s) and allowed to sit for a period of time, e.g., from about 5 minutes to about 48 hours, e.g., about 30 minutes, about 1 hour, about 2 hours, about 4 hours, about 8 hours, about 12 hours, about 24 hours, or about 48 hours.

Additionally or alternatively, the inorganic binding agents may be selected according to a level of natural oxidation (e.g., upon exposure to environmental oxidants over a period of time). For example, inorganic binding agents may have differing levels of oxidation depending on the geographic location from which the binding agent is procured (e.g., natural clay deposit). Further, the depth of the inorganic binding agent below the surface may also affect the level of oxidation of the inorganic binding agent. For example, clay minerals at the surface level or close to the surface typically have greater exposure to atmospheric oxidants such as oxygen, ozone, and/or atmospheric radicals (e,g., OH, NO₂, etc.) and are expected to be more oxidized relative to clay minerals deeper underground.

The inorganic binding agents may undergo oxidation through heat treatment, e.g., during the casting process. Thus, for example, inorganic binding agents that have been at least partially oxidized by the casting process may be recycled into new binder compositions.

The oxidation state of various components of the inorganic binding agent may be used to assess its relative degree of oxidation. For example, clay minerals such as bentonite typically comprise iron, which may be present in different oxidation states, specifically Fe²⁺ (ferrous iron), and Fe³⁺ (ferric iron). The relative concentrations of ferrous and ferric iron may be used to assess the amount of oxidation, e.g., redox state, of the bentonite. The concentrations of Fe²⁺ to Fe³⁺ may be determined by measuring the acid soluble iron content of the inorganic binding agent.

The acid soluble iron contents (as an indication of the relative degree of oxidation) can be determined according to the following procedure. A 2 g sample of the clay is mixed with 50 ml of 0.5 H₂SO₄ solution in a 50-ml Nelgene vial. After settlement of the bentonite particles, a 0.25 ml aliquot of the supernatant is pipetted into a 50-ml vial, and 25 ml of deionized water was added. A 1 ml aliquot of FerroZine™ (sodium 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine-4′,4″-disulphonate) indicator is then added and mixed. The resulting colored complex formed between ferrous ion (Fe²⁺) and FerroZine™ is measured by a spectrophotometer to calculate the amount of soluble ferrous iron against a soluble iron calibration curve. About 200 mg of ascorbic acid is then added to the solution (to reduce Fe³⁺ to Fe²⁺), and the resulting color measured as the total iron content of the clay.

In some non-limiting examples, the inorganic binding agent may comprise from about 270 ppm to about 335 ppm Fe²⁺ and from about 525 ppm to about 700 ppm Fe³⁺ (e.g., a ratio of Fe²⁺ to Fe³⁺ ranging from about 0.4 to about 0.6). For example, the inorganic binding agent may comprise from about 300 ppm to about 315 ppm Fe²⁺ and from about 575 ppm to about 635 ppm Fe³⁺. These ranges are exemplary only, wherein a greater amount of Fe³⁺ relative to Fe²⁺ provides an indication of a more oxidized material.

According to some aspects of the present disclosure, the ratio of Fe²⁺ to Fe³⁺ (Fe²⁺/Fe³⁺) of the inorganic binding agent may be less than 1.2, such as less than 1.0, less than 0.9, less than 0.8, less than 0.7, less than 0.6, or less than 0.5. For example the ratio of Fe²⁺ to Fe³⁺ of the inorganic binding agent may range from about 0.5 to about 1.5, from about 0.75 to about 1.25, or from about 0.8 to about 1.2. In some examples, the ratio of Fe²⁺ to Fe³⁺ of the inorganic binding agent may be about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, about 1.0, or about 1.1.

In some aspects of the present disclosure, the binder composition may comprise at least one carbonaceous material. The carbonaceous material may be inorganic, organic, or a mixture thereof. Carbonaceous materials that may be useful in the compositions herein include, but are not limited to, coal (including lignite coal and bituminous coal, such as, e.g., sea coal), lignite, leonardite, graphite, anthracite, cellulose, and combinations thereof. In at least one example, the composition comprises coal, a combination of coal and graphite, or a combination of coal and lignite.

According to some aspects of the present disclosure, the total amount of carbonaceous material in the composition (e.g., binder composition) may range from about 0.1% by weight to about 30% by weight. For example, the composition may comprise from about 1% by weight to about 25%, from about 2% by weight to about 22% by weight, from about 5% by weight to about 20% by weight, from about 7.5% by weight to about 17.5% by weight, or from about 10% by weight to about 15% by weight of the carbonaceous material, relative to the total weight of the composition.

In some aspects of the present disclosure, the composition comprises coal, e.g., in an amount ranging from about 5.0% by weight to about 25.0% by weight of the total composition, such as, e.g., from about 7.5% by weight to about 20.0% by weight, from about 8.0% by weight to about 18.0% by weight, from about 9.0% by weight to about 15.0% by weight, or from about 10.0% by weight to about 12.5% by weight of the total composition.

In some aspects of the present disclosure, the carbonaceous material(s) may he at least partially oxidized. For example, the carbonaceous material may be oxidized by exposure to (e.g., reaction with) one or more oxidation agents. Thus, for example, at least the outermost surface of the carbonaceous material (e.g., surfaces of carbonaceous particles) may be treated by exposure to one or more oxidation agents, providing oxidized carbonaceous particles. Exemplary oxidation agents include, but are not limited to, hydrogen peroxide (H₂O₂), oxygen (O₂), ozone (O₃), and soda ash (Na₂CO₃). In some examples, a combination of two or more oxidation agents, including the foregoing oxidation agents, may be used. In at least one example, the carbonaceous material comprises coal particles that have been oxidized by exposure to hydrogen peroxide, soda ash, or both hydrogen peroxide and soda ash. In at least one example, the carbonaceous material comprises coal particles that have been oxidized by exposure to an oxidant in aqueous solution.

The carbonaceous materials may be oxidized by any suitable method. For example, an oxidation agent may be mixed or mulled with the carbonaceous material and the resulting mixture allowed to set for a period of time (e,g., at least 5 minutes, 15 minutes, 30 minutes, 1 hour, 2 hours, 3 hours, 6 hours, 12 hours, 18 hours, 24 hours, 30 hours, 36 hours, 42 hours, or 48 hours). In some examples, the carbonaceous material is placed in contact with an oxidation agent for a number of days, such as, e.g., at least one day, at least 3 days, at least 5 days, at least 10 days, or at least 15 days. Additionally or alternatively, the oxidation agent may contact the carbonaceous material for a period of time ranging from about 1 day to about 12 days, from about 2 days to about 10 days, from about 3 days to about 9 days, or from about 4 days to about 8 days.

The amount of oxidation agent may range from about 0.01% to about 10.0% by weight with respect to the weight of the carbonaceous material, such as, from about 0.02% to about 8% by weight, from about 0.05% to about 5.0% by weight, or from about 1% to about 3% by weight, with respect to the weight of the carbonaceous material. For example, the ratio of the weight of the oxidation agent to the weight of the carbonaceous material may range from about 1:100 to about 1:10, such as, e.g. from about 1:75 to about 1:15, or from about 1:50 to about 1:25.

In some aspects of the present disclosure, the carbonaceous material may be treated with a solution comprising from about 0.1% by weight to about 15% by weight of the oxidation agent. For example, the solution may comprise from about 0.2% by weight to about 12% by weight, from about 0.5% by weight to about 11% by weight, from about 1% by weight to about 10% by weight, or from about 2% by weight to about 8% by weight of the oxidation agent. In at least one example, the solution may comprise about 3% hydrogen peroxide by weight. In some examples, the solution may comprise less than about 10% by weight soda ash, such as, e.g., about 9%, about 8%, about 7%, about 6%, about 5%, about 4%, about 3%, about 2%, or about 1% by weight. Additionally or alternatively, the carbonaceous material may be treated with a solution (such as, e.g., an aqueous solution) comprising more than one oxidation agent.

In some examples, the carbonaceous material(s) may be oxidized with heat treatment. For example, carbonaceous materials may be at least partially oxidized through exposure to oxygen and elevated temperatures during sand casting, and these oxidized carbonaceous materials may be at least partially recovered for reuse.

The compositions herein may further comprise one or more high aspect ratio silicates. The aspect ratio (ρ) of a particle may be defined as the length along the particle's major axis divided by the width. The term “high aspect ratio silicate” includes silicate minerals having an aspect ratio of at least 10, such as, e.g., an aspect ratio between 10 and 1000. For example, the compositions herein may comprise a silicate having an aspect ratio ranging from about 10 to about 500, from about 10 to about 250, from about 10 to about 200, from about 10 to about 150, from about 20 to about 100, from about 20 to about 80, from about 30 to about 100, from about 40 to about 100, from about 40 to about 80, or from about 50 to about 70, e.g., an aspect ratio of about 20, about 25, about 30, about 35, about 40, about 45, about 50, about 55, about 60, about 65, about 70, about 75, or about 80.

Exemplary high aspect ratio silicates suitable for the compositions herein include, but are not limited to, mica and talc. Mica minerals suitable for the compositions herein include, but are not limited to, muscovite, paragonite, phlogopite, biotite, and combinations thereof.

Binder compositions according to the present disclosure may comprise from about 0.1% to about 5.0% by weight of a high aspect ratio silicate, with respect to the total weight of the binder composition, such as from about 0.1% to about 4.8% by weight, from about 0.2% to about 4.5% by weight, from about 0.5% to about 4.0% by weight, from about 0.8% to about 3.8% by weight, from about 1.0% to about 3.5% by weight, from about 1.2% to about 3.0% by weight, from about 1.5% to about 3.0% by weight, from about 1.8% to about 2.8% by weight, or from about 2.0% to about 2.5% by weight. For example, the binder composition may comprise about 0.5%, about 1.0%, about 1.2%, about 1.5%, about 1.8%, about 2.0%, about 2.1%, about 2.2%, about 2.3%, about 2.4%, or about 2.5% by weight of a high aspect ratio silicate, with respect to the total weight of the hinder composition.

As mentioned above, the compositions herein may be binder compositions, e.g., suitable for combining with an aggregate to prepare green sand. In some aspects of the present disclosure, the binder composition may comprise from about 70% by weight to about 90% by weight of at least one inorganic binding agent, from about 0.1% to about 30% by weight of at least one carbonaceous material, and from about 0.1% by to about 5.0% by weight of at least one high aspect ratio silicate, with respect to the total weight of the composition. For example, the binder composition may comprise from about 75% by weight to about 85% by weight of the inorganic binding agent(s), from about 1% by weight to about 25% by weight, from about 5% by weight to about 22% by weight, or from about 10% by weight to about 15% by weight of the carbonaceous material(s), and from about 1% by weight to about 4% by weight, or from about 2% by weight to 3% by weight of the high aspect ratio silicate material(s), with respect to the total weight of the binder composition. in some examples, the inorganic binding agent comprises bentonite, e.g., sodium and/or calcium bentonite, and the carbonaceous material comprises coal. In some examples, the high aspect ratio silicate comprises mica.

According to some aspects of the present disclosure, at least one of the inorganic binding agent and the carbonaceous material, or both, may be at least partially oxidized. In at least one example, the inorganic binding agent (or at least one of two or more inorganic binding agents) and the carbonaceous material (or at least one of two or more carbonaceous materials) are both oxidized. The inorganic binding agent and the carbonaceous material may be oxidized separately before combining the two materials to produce the binder composition, or may be oxidized at the same or substantially the same time.

In at least one example, the carbonaceous material is first oxidized (e.g., by exposure to one or more oxidants), and then the oxidized carbonaceous material is combined with an inorganic binding agent. In further examples, the inorganic binding agent and the carbonaceous material are first combined, and then the resulting mixture is oxidized, e.g., by exposure to one or more oxidants. A high aspect ratio silicate optionally may be combined with the oxidized carbonaceous material before, after, or at the same time as combining the oxidized carbonaceous material with the inorganic binding agent.

The amount of volatile organic matter and/or water of the binder compositions herein may be measured via VOC and loss on ignition (LOI) testing. The VOC and LOI measurements may be conducted according to AFS standards and testing procedures (AFS Mold and Core Test Handbook). VOC refers to a measurement of the amount of material in the composition that will volatize at a temperature of 900° F. (482° C.). The LOI value refers the difference in weight of a material before and after heating it at a high temperature (“igniting” the material), in particular the temperatures used during casting, e.g., 982° C. (˜1800° F.) according to APS 5100-00-S. The LOI value indicates of the amount of combustible material in the green sand composition, e.g., organic material, that may decomposes upon heating to the temperatures present during casting.

In some examples, the binder composition may have a VOC content ranging from about 13.0% to about 18.5% by weight, such as, e.g., from about 13.5% to about 18% by weight, from about 14% to about 17.5% by weight, or from about 14.5% to about 17% by weight. Additionally or alternatively, the binder compositions herein may exhibit a LOI value ranging from about 22% to about 27%, such as, e.g., about 23%, about 24%, about 25%, or about 26%.

The binder compositions herein may be combined with at least one aggregate and water to produce a green sand composition. The term “aggregate” as used herein includes homogeneous materials, e.g., particles each comprising the same or substantially the same composition, as well as heterogeneous or composite particles, e.g., comprising materials of different compositions aggregated into a single particle. Aggregates suitable for the compositions herein include, e.g., natural and synthetic sand, and sand composite materials. Examples of aggregates that may be used in the compositions herein include, but are not limited to, silica sand (SiO₂), chromite sand (FeCr₂O₄), and zircon sand (ZrSiO₄), any of which optionally may include other elements such as magnesium, aluminum, manganese, and/or carbon (e.g., graphite). Other types of sand and other aggregates are likewise contemplated and may be used in the compositions herein without departing from the principles of the present disclosure.

In some aspects of the present disclosure, the green sand composition may comprise at least 70% by weight of at least one aggregate with respect to the total green sand composition, such as, e.g., at least 75% by weight, at least 80% by weight, at least 85% by weight, or at least 90% by weight, from about 70% to about 90% by weight of at least one aggregate, with respect to the total weight of the composition, such as from about 72% to about 88% by weight, from about 74% to about 84% by weight, or from about 76% to about 82% by weight, with respect to the total weight of the composition.

The green sand may further comprise water providing for a moisture content ranging from about 2.75% to about 6.25% by weight with respect to the total weight of the green sand composition. For example, the green sand composition may have a moisture content ranging from about 2.94% to about 5.08% by weight, from about 3.13% to about 5.43% by weight, from about 4.19% to about 5.08% by weight, from about 4.33% to about 5.94% by weight with respect to the total weight of the green sand composition. Before the green sand composition has been processed under a casting procedure, the moisture content of the composition may range from about 2.94% to about 3.16% by weight, from about % to about % by weight, or from about % to about % by weight. For example about 2.90%, 2.92%, 2.94%, 2.96%, 2.98%, 3.00%, 3.02%, 3.04%, 3.06%, 3.08%, 3.10%, 3.12%, or 3.14% by weight with respect to the total weight of the green sand composition.

Green sand compositions prepared from binder compositions of the present disclosure (e.g., comprising inorganic binding agent(s) and carbonaceous material(s)) may comprise from about 5% to about 20%, from about 8% by weight to about 16% by weight, or about 10% by weight to about 15% by weight of a binder composition with respect to the total weight of the green sand composition. For example, the green sand composition may comprise from about from about 70% to about 90% by weight of at least one aggregate, from about 5% to about 20% of a binder composition (e.g., comprising inorganic binding agent(s) and carbonaceous material(s)), and from about 2.75% to about 6.25% by weight water moisture.

Performance of green sand compositions may be analyzed according to a series of properties of the green sand compositions. For example, green sands may be characterized or evaluated by such properties as VOC, LOI, moisture content, compactability, permeability, wet tensile strength, green shear strength, methylene blue uptake, and/or AFS clay content, among other properties. These measurements are typically executed according to AFS standards and testing procedures (AFS Mold and Core Test Handbook).

Generally testing of green sand compositions is performed on a specimen shaped as a cylinder having a diameter of 50.8 mm (2 in.) and a height of 50.8 mm (i.e., a cylindrical sample 2 in. by 2 in.), or a cylinder having a diameter of 50 mm and a height of 50 mm. Green sand compositions prepared from the binder compositions herein may be tested for VOC and LOI measurements, as described above. Green sand compositions according to the present disclosure may have a VOC content ranging from about 1.8% to about 2.4% by weight, such as from about 2.0% to about 2.2% by weight. The LOI levels of the green sand compositions herein may range from about 3.5% to about 4.5% by weight, from about 3.7% to about 4.2% by weight, or from about 3.8% to about 4.0% by weight.

Green compression strength refers to the pressure required to rupture a sample at compressive loading. Green sand compositions according to the present disclosure may have a green compression strength ranging from about 20.0 N/cm² to about 35.0 N/cm², such as from about 21.0 N/cm² to about 32.0 N/cm², from about 2.1.5 N/cm² to about 31.0 N/cm², from about 22.0 N/cm² to about 30.5 N/cm², from about 22.5 N/cm² to about 30.0 N/cm², or from about 24.0 N/cm² to about 27.5 N/cm².

Green shear strength refers to the stress required to rupture a sample under a shear load, e.g. a transverse force. Green sand compositions according to the present disclosure may have a green shear strength ranging from about 2.4 N/cm² to about 4.0 N/cm², such as from about 2.6 N/cm² to about 3.8 N/cm², from about 2.7 N/cm² to about 3.6 N/cm², from about 2.9 N/cm² to about 3.5 N/m², from about 3.1 N/cm² to about 3.4 N/cm².

Wet tensile strength is a useful metric for determining the ability of the sand mold to resist scabbing, or the undesirable formation of projections or roughness on casted articles. During casting, water from the sand adjacent to the molten metal is driven back, creating a condensation zone between the dry and wet sand. The strength of the sand in this layer is considered the wet tensile strength. Higher wet tensile values correspond to less propensity towards scabbing. Green sand compositions according to the present disclosure may have a wet tensile strength at ambient temperature (˜25° C.) ranging from about 0.300 N/cm² to about 0.510 N/cm², such as from about 0.302 N/cm² to about 0.432 N/cm², from about 0.308 N/cm² to about 0.400 N/cm², from about 0.333 N/cm² to about 0.395 N/cm², or from about 0.340 N/cm² to about 0.386 N/cm².

Compactability (also referred to as “compressibility”) measures the change in volume of green sand on compaction. Compactability is measured as the percentage height decrease of a sample after the applying a pressure of about 140 psi to the sample for three seconds. Green sand compositions according to the present disclosure may have a compactability ranging from about 43.5% to about 47.5%, such as from about 44.0% to about 47.0%, from about 44.5% to about 46.5%, or from about 45.0% to about 46.0%.

The methylene blue (mL) test is a measurement of the amount of inorganic binding material, e.g. clay, with the ability to absorb water remaining in the green sand composition. The ability of inorganic binding materials to absorb water affects the strength of molds prepared from the green sand composition. Exemplary binder compositions according to the present disclosure have methylene blue levels ranging from about 47 mL to about 65 mL, such as, from about 49 mL to about 63 mL, from about 51 mL to about 61 mL, from about 53 mL to about 59 mL, or from about 53 mL to about 57 mL.

AFS Clay content test indicates the amount of fines and water absorbing material in the green sand composition. The test typically measures the amount of clay in a 50 g specimen of green sand, by repeated stirring and washing with water and dilution with caustic soda. The difference between the initial weight of the specimen and the final dry weight of the specimen is multiplied by 2 to give the AFS Clay content. Exemplary green sand compositions according to the present disclosure may have an AFS Clay measurement ranging from about 9.0% to about 11.5%, from about 9.4% to about 11%, from about 9.6% to about 10.8%, from about 9.8% to about 10.5%, or from about 10.0% to about 10.3%.

Casting of materials releases a variety of emissions, e.g, gases and particulates, including VOCs. Most of these emissions are released during the pouring, cooling, and shake out stages of the casting process. Typical emissions from the casting process include, but are not limited to, water vapor, CO, CO₂, CH₄, and BTEX (benzene, toluene, ethylbenzene and xylene) gases. These emissions may be measured by the mass of the emitted compound compared to the mass of the binder composition used to prepared the green sand composition (e.g., an exemplary binder composition comprising an inorganic binding agent, carbonaceous materials, and optionally a high aspect ratio silicate).

In some examples, the emissions level of BTEX of the green sand compositions herein may be less than 0.15 mg BTEX produced per gram of the binder composition used to prepare the green sand composition, such as less than 0.12 mg/g, less than 0.10 mg/g, less than 0.08 mg/g, less than 0.06 mg/g, or less than 0.05 mg/g. For example, the level of BTEX emissions may range from about 0.01 mg/g to about 0.10 mg/g with respect to the weight (in grams) of BTEX produced per gram of the binder composition, such as, e.g., form about 0.02. mg/g to about 0.09 mg/g, from about 0.03 mg/g to about 0.07 mg/g, or from about 0.02 mg/g to about 0.06 mg/g.

The emission of CO₂ of the green sand compositions herein may be less than about 7.2 mg per gram of the binder composition used to prepare the green sand composition. For example, the green sand compositions may emit between 3.13 mg to about 7.20 mg, from about 3.29 mg to about 6.99 mg per gram of the binder composition used to prepare the green sand composition.

In additional or alternative aspects of the present disclosure, the emissions of CO of the green sand compositions herein may be less than about 2.18 mg per gram of the binder composition used to prepare the green sand, such as, less than 2.15 mg/g, less than 2.00 mg/g, less than 1.90 mg/g, less than 1.80 mg/g, or less than 1.75 mg/g. For example, the level of CO emissions may range from about 1.65 mg/g to about 2.20 mg/g, from about 1.84 mg/g to about 2.15 mg/g.

Additionally or alternatively, the emissions of methane (CH₄) of the green sand compositions herein may be less than 0.5 mg per gram of the binder composition used to prepare the green sand composition. For example the level of CH₄ emissions may range from about 0.18 mg/g to about 0.24 mg/g, from about 0.19 mg/g to about 0.21 mg/g.

Aspects of the present disclosure are further illustrated by reference to the following, non-limiting numbered paragraphs describing exemplary embodiments.

1. A binder composition comprising a carbonaceous material, an inorganic binding agent, and a high aspect ratio silicate, wherein at least one of the carbonaceous material or the inorganic binding agent is oxidized.

2. A binder composition comprising a carbonaceous material and an inorganic binding agent, wherein the inorganic binding agent is oxidized, such that the inorganic binding agent has a ratio of Fe²⁺ to Fe³⁺ less than 1.2.

3. A binder composition comprising an oxidized carbonaceous material and an inorganic binding agent, wherein the oxidized carbonaceous material is prepared by treatment with an oxidation agent.

4. The composition according to paragraph 3, wherein the oxidation agent comprises soda ash, hydrogen peroxide, ozone, or a combination thereof.

5. The composition according to any of paragraphs 1-4, wherein a ratio of Fe²⁺/Fe³⁺ of the inorganic binding agent is less than 1.

6. The composition according to any one of paragraphs 1-5, wherein the inorganic binding agent comprises sodium bentonite, calcium bentonite, or a mixture thereof.

7. The composition according to any one of paragraphs 1-6, wherein the composition comprises from about 70% by weight to about 90% by weight of the inorganic binding agent.

8. The composition according to any one of paragraphs 1-7, wherein the carbonaceous material or oxidized carbonaceous material comprises oxidized coal (e.g., oxidized lignite coal, oxidized bituminous coal, or oxidized sea coal), oxidized lignite, oxidized leonardite, oxidized graphite, oxidized anthracite, oxidized cellulose, or a combination thereof.

9. The composition according to any one of paragraphs 1-8, wherein the composition comprises from about 0.1% by weight to about 20.0% by weight of the carbonaceous material or the oxidized carbonaceous material.

10. The composition according to any one of paragraphs 2-9, further comprising a high aspect ratio silicate.

11. The composition according to paragraph 1 or 10, wherein the high aspect ratio silicate comprises mica or talc.

12. The composition according to any one of paragraphs 1, 10, or 11, wherein the composition comprises from about 0.1% by weight to about 5.0% by weight of the high aspect ratio silicate.

13. The composition according to paragraphs 1 or 10-12, wherein the high aspect ratio silicate comprises muscovite, paragonite, lepidolite, phlogopite, biotite, or a combination thereof.

14. A green sand composition comprising the binder composition of any one of paragraphs 1-13 and an aggregate.

15. The green sand composition according to paragraph 14, wherein the aggregate comprises silica sand, zircon sand, an aluminosilicate, or a mixture thereof.

16. A method of preparing a foundry composition, the method comprising preparing a binder composition of any one of paragraphs 1-13, optionally by oxidizing a carbonaceous material, and combining the oxidized carbonaceous material with an inorganic binding agent.

17. The method according to paragraph 16, wherein oxidizing the carbonaceous material includes treating the carbonaceous material with an oxidization agent.

18. The method according to paragraph 17, wherein the oxidization agent comprises soda ash, hydrogen peroxide, ozone, or a combination thereof.

19. The method according to any one of paragraphs 16-18, further comprising combining the oxidized carbonaceous material with a high aspect ratio silicate before, after, or at the same time as combining the oxidized carbonaceous material with the inorganic binding agent.

20. The method according to any one of paragraphs 16-19, wherein a ratio of Fe²⁺ to Fe³⁺ of the inorganic binding agent is less than 1.2 or less than 1.

21. The method according to any one of paragraphs 16-20, further comprising adding an aggregate and water to the binder composition to form a green sand composition, optionally wherein the green sand composition has a green compression strength ranging from about 21.5 N/m² to about 30.5 N/m².

22. The method according to paragraph 21, wherein the green sand composition has a green shear strength ranging from about 2.5 N/m² to about 3.7 N/m².

23. A method of molding an article, the method comprising introducing a heated material into a mold, wherein the mold comprises a mixture of a carbonaceous material, an inorganic binding agent, a high aspect ratio silicate, water, and an aggregate, wherein at least one of the carbonaceous material or the inorganic binding agent is oxidized, and allowing the heated material to cool.

24. The method according to paragraph 23, wherein the mold releases less than 0.10 mg/g BTEX after introducing the heated material into the mold.

25. The method according to paragraph 23 or 24, wherein the carbonaceous material comprises oxidized coal.

26. The method according to any one of paragraphs 23-25, wherein the high aspect ratio silicate comprises mica or talc.

27. Use of a binder composition according to any one of paragraphs 1-13 and/or a green sand composition according to paragraph 14 or 15 to reduce emissions during casting.

The use according to paragraph 27, wherein the emissions comprise BTEX.

Other aspects and embodiments of the present disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the embodiments disclosed herein.

EXAMPLES

The following examples are intended to illustrate the present disclosure without, however, being limiting in nature. It is understood that the present disclosure encompasses additional aspects and embodiments consistent with the foregoing description and following examples.

Example 1

Four types of binder compositions were prepared to study the effect of oxidation on emissions during casting. Each binder composition comprised 80% bentonite and 20% coal by weight. Compositions 1 and 4 were prepared with natural sodium bentonite (commercial BPM National Standard). Compositions 2 and 3 were prepared using bentonite having a higher level of oxidation than the bentonite used in Compositions 1 and 4. Compositions 1 and 2 were prepared using commercial coal. Compositions 3 and 4 were prepared with oxidized coal, wherein three different variations of Composition 4 were prepared. Specifically, the oxidized coal was prepared by mixing 25 lbs. of the same type of commercial coal used in compositions 1 and 2 with one of three oxidizing solutions: a solution of 10% solution soda ash, a solution of 3% hydrogen peroxide, or room temperature water. In each case, the coal was placed in the oxidizing solution and allowed to sit for 10 days, after which the oxidized coal was washed with water. The oxidized coal was then dried in an oven at 225° F. until the moisture content of the oxidized coal was below 3%. Compositions 14 are summarized in Table 1 below.

TABLE 1 Binder Oxidized Oxidized composition Bentonite bentonite Coal coal 1 80% wt. — 20% wt. — 2 — 80% wt. 20% wt. — 3 — 80% wt. — 20% wt. 4 80% wt. — — 20% wt.

Example 2

Each of compositions 1-4 was combined with sand and water to prepare corresponding green sand compositions 1-4 for measuring green sand properties and emissions during sand casting. Each green sand composition to was prepared by combining sand with 9% by weight of the bentonite, with respect to the total weight of the green sand composition, and 1.8% by weight of the coal, with respect to the total weight of the green sand composition. Then water was added to achieve 42-48% compactability. Green sand properties (green compressive strength, green shear strength, wet tensile strength, permeability, methylene blue, and AFS Clay) were measured before casting according to AFS standards and testing procedures (AFS Mold and Core Test Handbook).

For test casting, a test mold was created from each of the green sand compositions 1-4, and a molten metal was poured into the mold. After cooling, the metal was removed, and the green sand was recycled for another test casting. Each green sand composition was heated for four test casting cycles, and the green sand properties of each green sand composition were measured after each heating cycle according to the same AFS standards and testing procedures. Data are as reported in Tables 2-5.

TABLE 2 Properties of green sand composition 1 Before casting Cycle 1 Cycle 2 Cycle 3 Cycle 4 Moisture Content 2.92% 4.08% 4.57% 5.62% 6.56% Compactability 44 47 44 46 47 Specimen Weight (g) 163 165 167 172 171 Green Comp. (N/m²) 17 14.8 17.7 12.9 15.3 Permeability 92 99 71 64 95 Wet Tensile (N/m²) 0.463 0.384 0.351 0.317 0.256 Green Shear (N/m²) 5.2 4.7 5.3 4.3 4.9 Methylene Blue (mL) 44 45 44 48 55 AFS Clay Content 9.0% 9.2% 9.0% 9.8% 11.25%

TABLE 3 Properties of green sand composition 2 Before casting Cycle 1 Cycle 2 Cycle 3 Cycle 4 Moisture Content 2.94% 3.85% 4.84% 5.32% 6.38% Compactability 45 47 44 44 46 Specimen Weight (g) 165 165 170 168 168 Green Comp. (N/m²) 15.7 19.4 14.7 16.7 18.3 Permeability 93 103 69 75 82 Wet Tensile (N/m²) 0.349 0.347 0.266 0.286 0.211 Green Shear (N/m²) 4.3 6 4.9 6.3 5.9 Methylene Blue (mL) 49 51 55 59 62 AFS Clay Content 9.0% 9.4% 10.1% 10.8% 11.40%

TABLE 4 Properties of green sand composition 3 Before casting Cycle 1 Cycle 2 Cycle 3 Cycle 4 Moisture Content 2.94% 4.33% 4.60% 4.94% 5.43% Compactability 47 46 46 47 45 Specimen Weight (g) 165 166 162 163 165 Green Comp. (N/m²) 21.5 22.1 25.1 24.2 30.3 Permeability 101 89 130 102 89 Wet Tensile (N/m²) 0.391 0.399 0.372 0.341 0.302. Green Shear (N/m²) 2.6 2.7 3.7 2.9 3.5 Methylene Blue (mL) 51 57 61 62 63 AFS Clay Content 9.0% 10.1% 10.8% 10.9% 11.1%

TABLE 5 Properties of green sand composition 4 Before Heat Heat Heat Heat casting cycle 1 cycle 2 cycle 3 cycle 4 Moisture Content 3.13% 4.19% 4.50% 5.08% 5.98% Compactability 47 44 44 44 44 Specimen Weight (g) 163 165 165 165 166 Green Comp. (N/m²) 25.5 26.5 30.5 29.7 27.1 Permeability 117 89 95 80 74 Wet Tensile (N/m²) 0.503 0.432 0.386 0.338 0.309 Green Shear (N/m²) 2.7 3.3 3.6 3.4 3.1 Methylene Blue (mL) 49 51 54 53 56 AFS Clay Content 9.0% 9.4% 9.9% 9.7% 10.3%

As shown in Tables 2-5, compositions 1-4 exhibited similar wet tensile strength. Compositions 3 and 4 exhibited improved green compression strength. Compositions 1 and 2 exhibited improved green shear strength. These results suggest that using oxidized clay and/or oxidized coal results in comparable or improved green sand properties.

After the four heating cycles, portions of about 5-10 g of each of compositions 1-4 were dried in a speed drier to sufficiently reduce the moisture content of the green sand composition Two samples, each weighing 1 g, of each dried sand composition were then tested to measure emissions of CO₂, CO, CH₄, H₂O and BTEX. Each sample was placed on a quartz glass crucible and inserted in a glass rod connected to a tube furnace (Ansyco). The tube furnace and the glass rod were filled with nitrogen. Before putting the sample into the tube furnace, initial measurements of the gasses emitted by the furnace were taken in order to record control measurements, that is, the amount of each emission gas that was present in the tube furnace prior to the addition of the sample. The control measurements were only recorded for the first sample tested or as needed to test the functionality of the tube furnace. The control measurements were recorded over a period of time ranging up to 5 minutes. Then, the glass crucible that contained the sample was led into the tube furnace, until the sample passed completely through the glass rod. The tube furnace maintained a temperature of about 900° C., while measuring emissions of BTEX, CO, and CH₄ of each sample using Fourier-Transform infrared spectroscopy (FT-IR Gasmet Analyzer), over a period of time ranging between 4 and 7 minutes, depending on the amount of gases that each sample released. The amount of gases emitted by the sample were observed on a monitor connected to the tube furnace that showed the amount of each gas emitted from the sample as a curve. Measurements of emitted gasses were taken until all curves tended to zero, at which time no further gases were being emitted from the sample. The area under each emission gas curve was calculated to determine the amount of each gas emitted over the measurement period. After the gas emissions of each sample were measured, the glass crucible with the sample was removed from the oven, and left at room temperature to cool. Once cooled, the remaining weight of the sample was measured.

The emissions data for the two samples of each composition were averaged to determine the mass of emissions of a particular gas per gram of the hinder composition used to prepare the corresponding green sand composition (mg/g). The emissions of CO₂, CO, CH₄, H₂O (water vapor), and BTEX are listed in Table 6.

TABLE 6 Emissions from green sand compositions CO₂ CO CH₄ H₂O BTEX Composition (mg/g) (mg/g) (mg/g) (mg/g) (mg/g) 1 2.9 2.0938 0.408 7.2191 0.21 2 7.72 2.9227 0.388 8.17253 0.14 3 7.09 2.1644 0.183 6.02197 0.08 4 3.21 1.7554 0.224 6.28957 0.06

The BTEX emissions for each binder composition are illustrated in FIG. 1. As shown in FIG. 1, the green sand compositions comprising oxidized coal (compositions 3 and 4) emitted lower amounts of BTEX as compared to the green sand compositions comprising commercial coal that had not been oxidized (compositions 1 and 2). Additionally, the compositions comprising oxidized bentonite (compositions 2 and 4) exhibited lower BTEX emissions than the green sand compositions comprising bentonite that had not undergone an oxidation process. These results suggest that using oxidized materials in binder compositions reduces the amount of certain emissions, e,g. BTEX, produced during casting.

It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the present disclosure being indicated by the following claims. 

1. A binder composition comprising: a carbonaceous material; an inorganic binding agent; and a high aspect ratio silicate; wherein at least one of the carbonaceous material or the inorganic binding agent is oxidized.
 2. A binder composition according to claim 1, wherein: the inorganic binding agent is an oxidized inorganic binding agent; and the inorganic binding agent has a ratio of Fe²⁺ to Fe³⁺ less than 1.2.
 3. A binder composition according to claim 1, wherein: the carbonaceous material is an oxidized carbonaceous material is prepared by treatment with an oxidation agent.
 4. The binder composition of claim 3, wherein the oxidation agent comprises soda ash, hydrogen peroxide, ozone, or a combination thereof.
 5. The binder composition of claim 1, wherein a ratio of Fe²⁺/Fe³⁺ of the inorganic binding agent is less than
 1. 6. The binder composition of claim 1, wherein the inorganic binding agent comprises sodium bentonite, calcium bentonite, or a mixture thereof.
 7. The binder composition of claim 1, wherein the composition comprises from about 70% by weight to about 90% by weight of the inorganic binding agent.
 8. The binder composition of claim 1, wherein the carbonaceous material comprises oxidized coal (optionally oxidized lignite coal, oxidized bituminous coal, or oxidized sea coal), oxidized lignite, oxidized leonardite, oxidized graphite, oxidized anthracite, oxidized cellulose, or a combination thereof.
 9. The binder composition of claim 1, wherein the composition comprises from about 0.1° A by weight to about 20.0% by weight of the carbonaceous material.
 10. (canceled)
 11. The binder composition of claim 1, wherein the high aspect ratio silicate comprises mica or talc.
 12. The binder composition of claim 1, wherein the binder composition comprises from about 0.1% A by weight to about 5.0% by weight of the high aspect ratio silicate.
 13. The binder composition of claim 1, wherein the high aspect ratio silicate comprises muscovite, paragonite, lepidolite, phlogopite, biotite, or a combination thereof.
 14. A green sand composition comprising the binder composition of claim 1 and an aggregate.
 15. The green sand composition of claim 14, wherein the aggregate comprises silica sand, zircon sand, an aluminosilicate, or a mixture thereof.
 16. A method of preparing a foundry composition, the method comprising preparing a binder composition by: oxidizing a carbonaceous material; and combining the oxidized carbonaceous material with an inorganic binding agent.
 17. The method of claim 16, wherein oxidizing the carbonaceous material includes treating the carbonaceous material with an oxidation agent.
 18. The method of claim 17, wherein the oxidation agent comprises soda ash, hydrogen peroxide, ozone, or a combination thereof.
 19. The method of claim 18, further comprising combining the oxidized carbonaceous material with a high aspect ratio silicate before, after, or at the same time as combining the oxidized carbonaceous material with the inorganic binding agent.
 20. The method of claim 16, wherein a ratio of Fe²⁺ to Fe³⁺ of the inorganic binding agent is less than 1.2.
 21. The method of claim 20, further comprising adding an aggregate and water to the binder composition to form a green sand composition, optionally wherein the green sand composition has a green compression strength ranging from about 21.5 N/m² to about 30.5 N/m² and a green shear strength ranging from about 2.5 N/m² to about 3.7 N/m². 22-26. (canceled) 